24 lines
990 B
C
24 lines
990 B
C
#include "cs.h"
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/* find nonzero pattern of Cholesky L(k,1:k-1) using etree and triu(A(:,k)) */
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int cs_ereach (const cs *A, int k, const int *parent, int *s, int *w)
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{
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int i, p, n, len, top, *Ap, *Ai ;
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if (!CS_CSC (A) || !parent || !s || !w) return (-1) ; /* check inputs */
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top = n = A->n ; Ap = A->p ; Ai = A->i ;
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CS_MARK (w, k) ; /* mark node k as visited */
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for (p = Ap [k] ; p < Ap [k+1] ; p++)
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{
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i = Ai [p] ; /* A(i,k) is nonzero */
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if (i > k) continue ; /* only use upper triangular part of A */
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for (len = 0 ; !CS_MARKED (w,i) ; i = parent [i]) /* traverse up etree*/
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{
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s [len++] = i ; /* L(k,i) is nonzero */
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CS_MARK (w, i) ; /* mark i as visited */
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}
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while (len > 0) s [--top] = s [--len] ; /* push path onto stack */
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}
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for (p = top ; p < n ; p++) CS_MARK (w, s [p]) ; /* unmark all nodes */
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CS_MARK (w, k) ; /* unmark node k */
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return (top) ; /* s [top..n-1] contains pattern of L(k,:)*/
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}
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